Image forming devices are comprised of a multitude of various electrical, mechanical, and optical devices. It is typically the case that all of the components of the image forming device must be properly installed for the image forming device to function properly. There are some exceptions. For instance, in an image forming device having a plurality of media trays, it may be possible for the image forming device to function properly if one or more trays are removed from the image forming device if there is at least one tray with a sufficient amount of media installed in the image forming device.
Similarly, it may be possible for color image forming devices to operate even though one or more toner cartridges is empty or completely removed. As an example, some color electrophotographic imaging devices have four developer cartridges, each cartridge containing a different color toner and perhaps other developer components such as a developer roll and a photoconductive member. A common color scheme found in color image forming devices uses cyan, magenta, yellow, and black developer cartridges. In color image forming devices such as these, it may be possible to operate in a black-only mode if one or more of the non-black developer cartridges is absent from the color image forming device. It is useful in such a scenario to detect the presence or absence of each of the toner cartridges to determine the allowable operating modes (e.g., black-only, full color, or partial color). Some common techniques for detecting the presence or absence of components include mechanical switches, optical sensors, and electrical or electromagnetic devices such as proximity sensors that use an RF or other distinctive signature. However, there are instances where the use of these types of detectors is impractical because of cost, space, or reliability concerns.